#backtotop {
  background-image: url(../returntop.png);
  background-repeat-x: no-repeat;
  background-repeat-y: no-repeat;
  background-attachment: initial;
  background-position-x: 50%;
  background-position-y: 0%;
  background-origin: initial;
  background-clip: initial;
  background-color: initial;
  bottom: 20px;
  cursor: pointer;
  display: none;
  height: 65px;
  position: fixed;
  right: 20px;
  text-indent: -9999px;
  width: 36px;
  z-index: 1;
}

#backtotop:hover {
  opacity: 0.8;
}

<!--[if lte IE 6]>
html {
  overflow-x: auto;
  overflow-y: hidden;
}

* html #backtotop {
  position:absolute;
}
<![endif]-->
